D’Angelo Harrison walked onto to the court at the John Lucas Camp in Houston this summer and promptly got his head handed to him.

There was no warm up period, per se. No skull session.

Lucas and his staff roll out the balls and bang! — some of the top college players and young pros in the nation go at it. Sometimes it’s 1-on-1. Sometimes it’s 3-on-3.

Harrison, the Red Storm’s sublime sophomore guard with the surreal shooting range and fueled by his mercurial emotional makeup, had games last season when he seemed lost in space in the first few minutes only to respond with a breathtaking final 35 minutes.

As Harrison adapts to his role as a lead guard — which he is better suited for at the NBA level — and steps out of the shadow of former teammate Maurice Harkless, his time this summer with Lucas and his staff should prove invaluable.

“What I saw in D’Angelo is a young man who is willing to work tremendously hard to make it to the next level but needed to understand what that really takes,’’ Lucas told The Post. “He’s at a national program and he had success last year, but there are countless players that were all-conference or their conference player of the year that are struggling for their professional basketball lives. I think D’Angelo saw just how hard you have to work — all the time.’’

Harrison arrived at St. John’s from the Houston area with the reputation of a player with unlimited shooting range and boundless competitive energy. He needed to learn to harness both, which he did through a freshman season in which he 16.8 points on 36 percent shooting on 3-pointers.

Now comes the next step. He is the most experienced returning player on a young, deep and talented St. John’s squad, which opens the season on Nov. 13 with a tough game against Detroit.

This should be Harrison’s team.

“I would look at film of myself sometimes last season and think, ‘What is that guy doing?’ ’’ Harrison said. “But I learned a lot last season and this summer. I expect to be more of a leader. I have to be for this team.’’

Harrison has the tools to make his name known among NBA talent evaluators. At 6-foot-3, 202 pounds, he has a point-guard frame, and there is no questioning his basketball IQ.

Proof of his emotional redlining last season, was the fact that he was called for just one technical foul. But first-half production (7.8 points on 34-percent shooting on from 3-point range) wasn’t nearly as proficient as his second-half output (9.2 points and 39-percent shooting behind the arc).

This summer the sophomore began his graduate work on taking the next step.

“He needed to see how far behind he was in his knowledge of the NBA language,’’ Lucas said.

For the first time in his life, Harrison found himself waiting as long as 10 minutes to get back on the court at Lucas’ camp. The promo on his website says it all.

You either play …or go home. There is no middle ground!

“I think the first day I was matched against Paul Pressey and Tyshawn Taylor,’’ Harrison said of Missouri’s point guard and Kansas’s former point guard. “It took me one day to figure it out. You better be ready the minute you step on the court.’’